Synthesis and characterization of diepoxyalkenes derived from (3Z,6Z,9Z)-trienes: lymantriid sex pheromones and their candidates

Identification of a unique three-component sex pheromone produced by the tea black tussock moth, Dasychira baibarana (Lepidoptera: Erebidae: Lymantriinae)

BACKGROUND

The tea black tussock moth Dasychira baibarana Matsumura is a devastating pest in tea plantations that causes substantial economic losses. Presently, there is no effective method to control this pest other than pesticide application. The identified sex pheromone of D. baibarana could be used for detecting and monitoring this pest.

RESULTS

Gas chromatography-electroantennogram detection showed that D. baibarana male moth antennae responded strongly to three components in the female sex pheromone gland, which were identified as: (3Z,6Z)-cis-9,10-epoxyhenicosa-3,6-diene (Z3,Z6,epo9-21:H) (I), (3Z,6Z,11E)-cis-9,10-epoxyhenicosa-3,6,11-triene (Z3,Z6,epo9,E11-21:H) (II) and (3Z,6Z)-henicosa-3,6-dien-11-one (Z3,Z6-21:11-one) (III). Dasychira baibarana uses a unique composition of an epoxydiene, epoxytriene, and dienone with the same 3,6-dienyl motif as its sex pheromone. The epoxytriene and dienone were not previously characterized as insect pheromone components. Electroantennogram analysis showed that each synthetic compound strongly stimulated male antennae, and compounds II and III elicited stronger responses than compound I. A wind tunnel bioassay and field trapping experiments proved that, ternary blends of compounds I-III attracted D. baibarana. Efficient attraction was achieved with a rubber septum baited with 500 μg of a mixture of compounds I-III at the ratio 25:20:55.

CONCLUSION

The three identified compounds elicited an electroantennogram response in D. baibarana male moth antennae, and a mixture of the three components at the ratio 25:20:55 attracted D. baibarana male moths in a wind tunnel assay and field trapping experiments. This blend could be used for integrated management of D. baibarana in tea plantations. © 2022 Society of Chemical Industry.

A nine carbon homologating system for skip-conjugated polyenes

Ozonolysis of Z,Z,Z-cylonona-1,4,7-triene leads to a 1,9-difunctionalised Z,Z-3,6-nonadiene which is readily converted into a range of polyunsaturated pheromones and fatty acids.

Characterization of posticlure and the structure-related sex pheromone candidates prepared by epoxidation of (6Z,9Z,11E)-6,9,11-trienes and (3Z,6Z,9Z,11E)-3,6,9,11-tetraenes

trans-11,12-Epoxy-(6Z,9Z)-6,9-henicosadiene (posticlure) has been identified from a pheromone gland of the lymantriid species, Orgyia postica. Since the diversity of Lepidoptera suggests that some species utilize the structure-related epoxy compound as a sex pheromone component, epoxydienes and epoxytrienes derived from (6Z,9Z,11E)-6,9,11-trienes and (3Z,6Z,9Z,11E)-3,6,9,11-tetraenes with a C19-C21 chain were systematically synthesized and the chemical data were accumulated in order to contribute to a new pheromone research. Peracid oxidation of each triene and each tetraene produced, respectively, a mixture of three epoxydienes (cis-6,7-epoxy-9,11-diene; cis-9,10-epoxy-6,11-diene; and trans-11,12-epoxy-6,9-diene) and four epoxytrienes (cis-3,4-epoxy-6,9,11-triene; cis-6,7-epoxy-3,9,11-triene; cis-9,10-epoxy-3,6,11-triene; and trans-11,12-epoxy-3,6,9-triene). While the 9,10-epoxy compounds were unstable and, interestingly, converted into 9-ketone derivatives after chromatography over SiO2, each positional isomer was isolated by HPLC equipped with an ODS column, and the chemical structure was determined by NMR analysis. On the GC-MS analysis with a DB-23 column, the positional isomers were also eluted separately and characteristic mass spectra were proposed. By comparing the spectral data of the epoxy compounds with a different carbon chain, diagnostic fragment ions reflecting the chemical structure were determined as follows: m/z 79, 109, 113, and M-114 for the 6,7-epoxydienes; m/z 69, 97, 111, 139, and M-111 for the 9,10-epoxydienes; m/z 57, 79, 109, 136, M-151, and M-111 for the 11,12-epoxydienes; m/z 79, 91, 105, and 119 for the 3,4-epoxytrienes; m/z 79, 124, M-124, M-96, and M-69 for the 6,7-epoxytrienes; m/z 79, 95, 109, 137, and M-108 for the 9,10-epoxytrienes; and m/z 79, 134, M-149, M-109, and M-95 for the 11,12-epoxytrienes.

Characterization of epoxytrienes derived from (3Z,6Z,9Z)-1,3,6,9-tetraenes, sex pheromone components of arctiid moths and related compounds

Cis-9,10-epoxy-(3Z,6Z)-1,3,6-henicosatriene has been identified from a pheromone gland of arctiid species, such as Hyphantria cunea. Since the diversity of lepidopteran species suggests that structurally related compounds of the 9,10-epoxide are also utilized as a sex pheromone components, epoxytrienes derived from (3Z,6Z,9Z)-1,3,6,9-tetraenes with a C(19)-C(21) chain were systematically synthesized and characterized. While 1,2-epoxy-3,6,9-triene was not obtained, peracid oxidation of each tetraene produced a mixture of three cis-epoxides (3,4-epoxy-1,6,9-triene, 6,7-epoxy-1,3,9-triene, and 9,10-epoxy-1,3,6-triene), which were separable by LC as well as GC. Detailed inspection of the mass spectra of the C(19)-C(21) epoxides indicated the following diagnostic ions for determining the chemical structures: m/z 79, M-70, and M-41 for the 3,4-epoxytrienes; m/z 79, 95, 109, and 149 for the 6,7-epoxytrienes; and m/z 79, 106, 120, M-121, and M-107 for the 9,10-epoxytrienes. Resolution of two enantiomers of each C(21) epoxytriene was accomplished by HPLC equipped with a chiral column, and analysis of the pheromone extracted from virgin females of H. cunea revealed the 9S,10R configuration of the natural epoxytriene as the same configuration of C(21) 9,10-epoxydiene, a main pheromone component of this species. GC-EAD analysis of the optically pure epoxides showed that the antennae of male H. cunea were stimulated more strongly (>100 times) by the (9S,10R)-isomers than the antipodes.

Chiral synthesis of (Z)-3-cis-6,7-cis-9,10-diepoxyhenicosenes, sex pheromone components of the satin moth, Leucoma salicis

All four isomers of (Z)-3-cis-6,7-cis-9,10-diepoxyhenicosenes, 1-4, have been synthesized using D-xylose as the chirally pure starting material. D-Xylose was first converted to 2-deoxy-4,5-O-isopropylidene-3-t-butyldimethylsilyl-D-threopentose 11, via several steps of selective protection, dehydroxylation, and deprotection. Wittig coupling of 11 with nonyltriphenylphosphonium bromide followed by hydrogenation and acid catalyzed deprotection of hydroxyl groups yielded the chiral (2R,3R)-1,2,3-triol, 14, which was used as the precursor for the C-8 to C-21 unit of the (Z)-3-cis-6,7-cis-9,10-diepoxyhenicosenes. Selective tosylation of 14 followed by stereospecific cyclization yielded (2R,3R)-1,2-epoxytetradecan-3-ol, 16, which was then divergently converted to the t-butyldimethylsilyl ether 17 and tosylate 22, respectively. Establishment of the C-5 through C-7 unit of the target molecules was accomplished via regiospecific coupling of 17 with 1-t-butyldimethylsiloxy-2-propyne to form 18. Stepwise transformation of 18 via the formation of tosylate 19, desilylation, and stereospecific cyclization to form epoxy alcohol 20, followed by P2-Ni reduction yielded a key intermediate, allylic epoxy alcohol (Z)-2-(5S,6R)-cis-5,6-epoxyheptadecen-1-ol, 21. Similarly, the coupling of 22 with 1-t-butyldimethylsiloxy-2-propyne yielded 23, which was stereospecifically cyclized to form 24. Desilylation and P2-Ni reduction of 24 gave the antipodal intermediate, (Z)-2-(5R,6S)-cis-5,6-epoxyheptadecen-1-ol, 26. Asymmetric epoxidation of antipodes 21 and 26 with (L)- or (D)-diethyl tartrates resulted in the formation of diepoxy alcohols 27 and 29 from 21, and 33 and 31 from 26, respectively. Tosylation of these diepoxy alcohols followed by coupling with lithium dibutenyl cuprate yielded the four stereoisomers of (Z)-3-cis-6,7-cis-9,10-diepoxyhenicosenes, 1-4. Analysis of the retention characteristics of these materials revealed that one or both of the S*,R*,S*,R* stereoisomers comprise the major pheromone component(s) of Leucoma salicis.

Identification of epoxyhenicosadiene and novel diepoxy derivatives as sex pheromone components of the clear-winged tussock moth Perina nuda

Four EAG-active components (A-D) were found in the solvent extract of virgin females of the clear-winged tussock moth, Perina nuda. The most abundant component (B, ca. 250 ng/female) was identified as (3Z,6S,7R,9Z)-6,7-epoxyhenicosa-3,9-diene by GC-MS analyses of the extract, chemical derivatization, and comparative chiral HPLC. Minor components also elucidated were (3Z,9Z)-cis-6,7-epoxyicosa-3,9-diene, (A); (3R,45,6S,7R,9Z)-3,4-6,7-diepoxyhenicos-9-ene, (C); and its 3S,4R,6S,7R isomer, (D); with amounts of 0.4, 5, and 8 ng/female, respectively. Component B showed weak attractiveness to male moths in the field. The attractiveness was significantly enhanced by addition of component(s) C and/or D. No males were captured with either the antipode of component B or its mixtures with the minor components. In this field test, noctuid Hypocala rostrata males were also attracted with the synthetic P. nuda pheromone.